3. Just introduces an extra couple of sources of bright-star flares. That piece of glass has 2 sides... Otherwise no major harm.
2. for the above reason, leave out
1. Presumably your Dad used the filter wheel with a mono astroCCD. Such CCDs normally have a sensitivity similar to a full-spectrum mod on a DSLR. Consequently I would expect that filters meant for use with a mono astroCCD will have UV/IR blocking. No need for your Luminous filter.
Try this simple test to learn a bit more how filters and modded DSLRs behave. Point you OTA at a blank wall during daytime. Set your DSLR to auto shutter speed (your OTA has a fixed aperture). Note down the shutter speed, let us assume it says 1/1000 second. Remove the Luminous filter and note down the new auto-shutter speed. I would expect it to be faster, perhaps around 1/2000 second. This is because a full spectrum mod has half of its sensitivity in the IR. Now insert the NB Ha filter (with the Luminous filter out). Your auto-shutter speed will now be slower because you have cut off most of the available wavelengths, visible and IR. I would expect the new auto-shutter speed to be roughly 3x slower, say, at 1/250 second. Now insert the Luminous filter in addition. Three possible outcomes: A. the new auto-shutter speed is only marginally slower, say, 1/200 second, indicating that your Luminous filter still passes Ha but does block IR. B. The auto-shutter speed is much slower, say, 1/50 second, indicating that your Luminous filter blocks Ha (i.e. a true visible-light only filter). or C. The auto-shutter speed is much slower because your Ha filter was passing IR.
I'll have to think of another test to distinguish between B and C... I expect you will get A. If not, just post all your shutter speeds and we'll go from there.